// メディアンカット
private unsafe ColorBox[] medianCut(ColorEntry[] colors, ArgbColor[] importantColors, int paletteSize) {
#if DEBUG
var stopWatch = new System.Diagnostics.Stopwatch();
stopWatch.Start();
#endif
ColorBox[] boxes = new ColorBox[paletteSize];
int boxCount = 0;
boxes[boxCount++] = new ColorBox(0, colors.Length - 1) ;
boxes[0].CalcWeight(colors, importantColors);
fixed (ColorEntry* table = colors)
while (boxCount < paletteSize) {
// 分散が最も大きなBoxを探す
int divIndex = -1;
int maxWeight = int.MinValue;
for (int i = 0; i < boxCount; i++) {
if (boxes[i].DivWeight >= maxWeight) {
maxWeight = boxes[i].DivWeight;
divIndex = i;
}
}
int minIdx = boxes[divIndex].ColorIndexMin;
int maxIdx = boxes[divIndex].ColorIndexMax;
int ch = boxes[divIndex].DivChannel;
// 中央値を決めて分割
int median = boxes[divIndex].MedianValue;
int l = minIdx;
int r = maxIdx;
do {
while (l + 1 < r && table[l].Color.Channels[ch] <= median) l++;
while (l < r - 1 && table[r].Color.Channels[ch] >= median) r--;
if (table[l].Color.Channels[ch] > table[r].Color.Channels[ch]) {
ColorEntry temp = table[l];
table[l] = table[r];
table[r] = temp;
}
} while (l + 1 < r);
ColorBox leftBox = new ColorBox( minIdx, l);
leftBox.CalcWeight(colors, importantColors);
boxes[divIndex] = leftBox;
ColorBox rightBox = new ColorBox( r, maxIdx);
rightBox.CalcWeight(colors, importantColors);
boxes[boxCount++] = rightBox;
}
#if DEBUG
Console.WriteLine("median cut ({0} msec).", stopWatch.ElapsedMilliseconds);
#endif
return boxes;
}
